Process of tanning hides



NOV. 15, V. WRANGE PROCESS OF TANNING HIDES Filed March 4, 1931 Hf/o rney Patented Nov. 15, 1932 UNITED STATES PANY OF SWEDEN PATENT OFFICE GEORG VIKTOR WRANGE, or s'rocKHoLM', SWEDEN, 'aSSIGNOR or oNnHALn r0 AKTIEIBOLAGET FRIBERGS HOGVAOUUMPUMP, or sTOcKHOLM, swEnnN, A com"- rnocnss OF TANNING HIDES Application filed March 4, 1931, Serial No. 5I9;923,7and in Sweden March 11, 1930.

The present invention relates to a process of tanning hides and the like, in which the material to be tanned is subjected, in a manner known in itself, to the influence of vacuum in a closed tank, while the tanning solution is caused to circulate through the said tank containing the material tobe tanned, by

means of a pump or the like, and in which vapours and the like drawn off during this vacuum treatment are condensed.

It has been found that with the vapours drawn ofi during the vacuum treatment some more or less volatile acids and other active substances contained in the tanning solution pass off, and the percentage of such substances in the solution is thus gradually decreased while the treatment proceeds. The present invention has for its purpose to remedy this difficulty, and is broadly characterized by that the condensate formed by condensing the vapours is reintroduced, accordprocess proceeds, directly into the tanning tank, so that the percentage of volatile acids in the tanning solution is maintained as constant as possible during the entire tanning process. 7

In the case that the material to be tanned enclosed in the tank is first heated to a suitable temperature and afterwards subjected to the influence of a high vacuum, before the tanning solution is introduced into the tank, the condensate separated from the vapours during this first vacuum treatment will principally contain water and other substances given off by the tanning material, which obviously are of no use during the tanning process.

In this case, therefore, the process is carried out, according to the invention, in such manner that the condensate separated during the first vacuum treatment is discharged to a condensate receptacle, whereas the condensate separated after the tanning solution is introduced into the tank, is reintroduced directly into the tanning tank.

In the accompanying drawing an embodiment of an apparatus for performing the process according to the invention, is illus trated by Way of example. Fig. 1 shows a mg as it is formed, and while the tanning tanning tank viewed from. the end, and Fig. 2

shows the same in side view.

. According to the construction illustrated,

the apparatus consists of a tanning tank 1 provided with a door 2 for inserting the material to be tanned, and at the bottom of which a pipe coil 3 is provided,into which steam may be admitted for heating the contents of the tank. A pump 4 serves to put the tanning solution in circulation through the tank, and communicates for this purpose with the lower portion of the tank through a suction pipe 5 provided with a shut-off valve, and with its upper portionthrough a pressure pipe 6. The suction side of the pump also communicates, through a pipe 7 provided with a shut-off valve, with a receptacle 8 provided below the'tank, so that the tanning solution prepared in said receptacle canbe pumped into the tank by means of said pump. The upper portion of the tank communicates through a pipe 9 with a condenser-10, which is connected through a pipe 11 with a vacuum pump, not illustrated.

From the lower portion of said condenser apipe 13 provided with a shut-off valve 12 leadsrto the tank 1, the end of said pipe 13 opening in the tank being preferably provided with a back valve, and a pipe 15 provided with a shut-off valve 14 leads to a condensate receptacle 16.

While the material to be tanned is treated with the tanning solution caused to circulate through the tank by means of the pump 4, the tank is all the time maintained under vacuum, and the vapours drawn off through the pipe 9 are condensed in the condenser 10. According to the invention the condensate thus formed is returned through the pipe 13 directly to the tanning tank 1, so that active acid constituents escaping with the vapours are immediately again reintroduced into the tanning solution, which thus retains its full tanning power. The valve 14 is of course closed during this operation, so that no condensate escapes to the condensate receptacle 16.

In the case when the material to betanned the influence of a high vacuum, before the tanning solution is admitted into the tank, the vapours given of]? duringthis first vacuum treatment by the material to be tanned are also condensed in the condenser 10. The condensate thus formed, however, contains principally water and other matter given off by the material to be tanned, and since thesev substances are of no use during the subse-o 10 quent tanning process, the condensate formed during this first vacuum treatment 1s d15- charged through the pipe 15 to the condensate I receptacle 16.

Of course, the valve 12 is then closed. W hen this preparatory treatment is completed, and the tanning solution is introduced into the tank, the pipe'l'5 is closed by means of the valve 14, and the valve 12 is opened, so that condensate formed during the following tanning process is reintroduced into the tank, and loss of active tanning agent is thus avoided. i

I claim: r V 1. In the process-of tanning hides and the like, whichconsists in subjecting the material to be tanned to the influence of vacuum and a circulating tanning solution, the steps of drawing ofi vapours and the like formed during such vacuum treatment and condens- 30 ing such vapours, and reintroducing such condensate according as it is formed and While the tanning process proceeds directly into the tanning solution, for the purpose of maintaining the percentage of volatile acids 3a in the tanning solution as constant as possible during the entire tanning process.

2. The process of tanning hides and the like, which consists in heating the material to-be tanned-to a suitable temperature, subecting the material to the influence of a high vacuum, drawing off vapours formed during such vacuum treatment and condensing such vapours, discharging the condensate formed to a condensate receptacle, afterwards subjecting the material to the influence of vacuum and a circulating tanning solution, drawing off vapours formed during such treatment and condensing such vapours, and reintroducing such condensate according as it is formed and while the tanning process proceeds directly into the tanning solution.

GEORG VIKTOR WRANGE. 

